Although vitamin D is an important fat-soluble vitamin that is essential in regulating calcium and phosphorous balance in a dog's body as well as promotes retention of calcium, thus aiding bone formation and nerve and muscle control, its excessive intake can lead to a condition known as vitamin D toxicity or vitamin D poisoning.
Puppies and young dogs are more prone to this condition although it can occur in dog of any age, size and breed.
Common symptoms of vitamin D toxicity are
Loss of appetite
Increased thirst (polydipsia)
Increased urination (polyuria)
Dark tarry feces containing blood
Blood in vomit
Loss of weight